This invention relates to a communication apparatus and a communication method which carry out wired transmission using a plurality of sub-carriers.
A transmission system using a plurality of sub-carriers such as an OFDM (Orthogonal Frequency Division Multiplexing) system is utilized for not only wireless communication but also wired communication. A transmission system using a plurality of sub-carriers has such an advantage that high quality communication becomes possible even in a harsh line. However, there is such a case that leakage electric power becomes greater, depending on quality of a transmission line and an influence is exercised on an outside.
In addition, in communication of the OFDM system, it is known a communication system which carries out transmission electric power control on a transmission side on the basis of an electric power measurement result on a reception side (see, Japanese Patent Publication JP-A-2003-152671). A system shown in the publication JP-A-2003-152671 obtains difference information between a reception electric power value of a sub-carrier which was detected on a reception side and a specified reception electric power and notifies it to a transmission side, in multi-carrier wireless communication, and controls transmission electric power of a sub-carrier on a transmission side which received the difference information. In addition, Japanese Patent Publication describes a technology for selecting a subcarrier to be used, depending on a state of a communication error detected on a reception side, in wired transmission of the OFDM system.
However, technologies shown in the Patent Publications JP-A-2003-152671 and JP-A-2003-218831 control transmission signals by utilizing a processing results of a reception signal on a reception side.
Japanese Patent Publication JP-A-2004-140565 describes a balance transmission apparatus which detects a balance component (mutually related with leakage electric power of a transmission line) from a voltage or a current of a conductor on a transmission side or a reception side, and carries out transmission control in such a manner that the detected unbalance component gets smaller.
However, Japanese Patent Publication JP-A-2004-140565 does not describe about a concrete method for transmission control based on an unbalance component.